Planetary power transmissions are used in both passenger vehicle and commercial vehicle applications. The powertrain in these vehicles generally includes an engine, a multi-speed transmission, and an output mechanism or differential.
The passenger vehicle of the past generally used a countershaft or synchronous-type transmission for providing the various speeds between the input and the output. Currently, both countershaft-type transmissions and planetary-type transmissions are employed in vehicle powertrains. In planetary-type transmissions, two or more planetary gearsets are controlled by a plurality of torque-transmitting mechanisms, commonly termed clutches and brakes to establish a plurality of speed ratios between a transmission input and a transmission output.
The planetary transmissions began as two-speed transmissions and developed into three-speed, four-speed, and five-speed type transmissions. Currently, there are a number of five-speed transmission units which are well known to the public, and also six-speed transmission units. One particular five-speed transmission is seen in U.S. Pat. No. 5,106,352 issued to Lepelletier on Apr. 21, 1992. The Lepelletier transmission incorporates an input gear mechanism or ratio-controlled set and an output planetary gearset, which provides a plurality of speed ratios. The Lepelletier concept employs five torque-transmitting mechanisms in the form of three rotating type or clutches and two stationary type or brakes.
It has become desirable more recently to incorporate six forward speed ratios in the planetary transmission, thereby improving the overall performance and economy of the passenger vehicle.